Surface electromyography-verified muscular damage associated with the opendorsal approach to the lumbar spine

The dorsal approach is increasingly preferred in the surgical treatment of vertebral fractures. However, the access and the implant's position cause m uscle loss, which can lead to instability and a reduced capacity for rehabi litation. Morphological factors (bones, intervertebral discs) are typically blamed for chronic pain syndromes in the literature, while less importance is attached to functional factors (muscles). The objective of this study w as therefore to investigate the isolated influence of dorsal spinal instrum entation on the back muscles by means of electromyography (EMG). A total of 32 patients with conditions after dorsal spondylodesis following the fract ure of a vertebral body and 32 subjects with healthy backs were enrolled in this study. The EMG signal was recorded in three different muscle groups d uring isometric extension exercise. The evaluation was performed by compari ng the mean rectified amplitudes of the three muscle groups in the patients and controls. The patients had significantly lower amplitudes in the multi fidus muscle (MF) and significantly higher amplitudes in the iliocostal mus cle (IL). Patients with severe pain were found to have lower electric muscl e potentials in all investigated muscle groups than patients with mild pain . The muscle damage which was established in the multifidus muscle is compe nsated by increased activity in the iliocostal muscle. On the basis of anat omical considerations, the damage pattern can be identified as having been caused by surgery. It is extremely unlikely that trauma is the cause.